EP1525460B1 - Device and method for generating pressure in the electrolytes of a reference electrode - Google Patents

Device and method for generating pressure in the electrolytes of a reference electrode Download PDF

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Publication number
EP1525460B1
EP1525460B1 EP03771059A EP03771059A EP1525460B1 EP 1525460 B1 EP1525460 B1 EP 1525460B1 EP 03771059 A EP03771059 A EP 03771059A EP 03771059 A EP03771059 A EP 03771059A EP 1525460 B1 EP1525460 B1 EP 1525460B1
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Prior art keywords
electrolyte
container
measuring probe
interior
measuring
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German (de)
French (fr)
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EP1525460A1 (en
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Andreas Derr
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Testo SE and Co KGaA
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Testo SE and Co KGaA
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/36—Glass electrodes

Definitions

  • the invention is applicable in the field of metrology and indeed in the measurement of charge carrier concentrations in liquids or solids.
  • the invention finds application in the measurement of a pH value.
  • the invention relates to a measuring probe for measuring a charge carrier concentration, in particular the pH value of a measuring substance, comprising a glass electrode containing a first electrolyte and a measuring electrode and having a container containing a second electrolyte, which with the glass electrode on the one hand and a reference electrode on the other hand is in communication, wherein the container has a diaphragm opening, by means of which the second electrolyte can communicate with the measuring substance.
  • the ph value is the negative decadic logarithm of the H + ion concentration (proton concentration) in a liquid.
  • This hydrogen ion concentration can be varied by addition of bases or acids to water within wide limits.
  • the measured value of the ph gives information about the strength of the acid or base.
  • the pH value can also be measured potentiometrically in addition to known chemically sensitive color indicators.
  • Various standard electrodes are known, whose electrode voltage can be converted to a reference electrode under the influence of a measuring substance in a measured ph value.
  • a known electrode used in laboratory technology is, for example, the hydrogen electrode.
  • glass electrode In practice, and in field use, however, has the so-called glass electrode Well proven because of its robustness.
  • Such a glass electrode has, in principle, a glass container whose glass outer wall is designed as a membrane and which contains a first electrolyte in its interior.
  • this first electrolyte is the so-called measuring or Ableitelektrode whose potential is measured relative to a reference electrode.
  • the reference electrode is embedded outside the glass container in a second electrolyte, which communicates with the glass membrane on the one hand and with the substance to be measured via a diaphragm on the other.
  • the diaphragm must be selected such that, on the one hand, the measuring substance in this area can come into contact with the second electrolyte, on the other hand, that the second electrolyte does not escape completely through the diaphragm. If the second electrolyte is slightly fluid, care must be taken that it does not flow out through the diaphragm.
  • the diaphragm may then be formed as a porous membrane. In the case of heavy-liquid or gel-like electrolytes, this problem is reduced and such electrodes can also be used in different measuring positions without the second electrolyte emerging.
  • the diaphragm may then have larger openings or be formed as an opening.
  • a measuring probe for measuring ph values which has a measuring electrode, a reference electrode and a second electrolyte in the form of a gel.
  • the second electrolyte is disposed in a container having a diaphragm in the form of an opening, at which the gel electrolyte can contact outwardly with a measuring substance.
  • the measuring electrode is an ion-sensitive field effect transistor.
  • the probe can be used to measure the ph value of rice grains to determine their age.
  • a ph probe is also known in which the potential of the measuring electrode is processed by means of an ion-sensitive field effect transistor. There, an electrolyte is connected by means of a diaphragm with a measuring liquid. Further measuring probes are for example in the DE 196 39 372 A1 and the WO 01/75430 A2 described.
  • the invention has for its object to extend as far as possible in a measuring probe of the type mentioned the possible duration of use with the same quality of measurement or to provide a way to make such a probe with little effort reusable.
  • the object is achieved according to claim 1, characterized in that the container has a pumping device for conveying a quantity of the second electrolyte into the interior of the container.
  • the pumping device can convey a certain amount of the second electrolyte into the interior of the container, so that an excess amount emerges from the diaphragm opening of the container.
  • This exiting amount of the second electrolyte either flows off or can be removed on the outside of the measuring probe, so that the second electrolyte is available in an unobstructed form at the diaphragm for subsequent measurements. Also contaminants are washed out by the exiting second electrolyte from the diaphragm opening with.
  • the invention provides that the container has, in the region of its wall, a channel filled with the second electrolyte, into which a body can be inserted in order to convey at least part of the second electrolyte located in the channel into the interior of the container.
  • a drive device which causes a displacement of the body to the interior of the container and that the drive means for replenishing the second electrolyte is decoupled from the body.
  • the drive device can be decoupled from the body for refilling the second electrolyte, it is possible, for example, to inject the second electrolyte under pressure into the container and thereby to return the body in the channel to its initial position by the hydrostatic pressure of the second electrolyte.
  • a particularly simple structural embodiment of the invention is that the body is a piston which slides in a hollow cylinder and that the drive means is formed with a screw.
  • the drive device can be operated without major application of force, as this takes place a strong reduction.
  • the volume to be displaced in the container is very small because of the usually small dimensions of the diaphragm opening, so that the piston does not have to travel a long way.
  • the drive device is designed such that the axis of the screw is perpendicular to the axis of the hollow cylinder and that the screw has at its tip a cone on which the piston is supported and its displacement in the direction of the axis of the screw by wedge action a shift of the piston causes.
  • the filling channel is connected to an externally closable feed channel, through which the probe the second electrolyte can be supplied.
  • the body may be inserted at least once into the container to displace or feed into the container a quantity of the second electrolyte, and thereafter upon retraction of the body through the feed channel, a quantity of the second electrolyte may be introduced into and from the filling channel Container nachbenumt be.
  • the inventive construction of the measuring probe proves to be particularly advantageous if the second electrolyte is formed by a gel. Then it is ensured that the probe can be operated in any position without a lot of the second electrolyte escaping through the opening of the diaphragm. Nevertheless, the gel as electrolyte has all the necessary properties for ionic conduction in a pH measuring probe. It is in addition to using thixiotroper Substances (gels) also conceivable to use difficult liquid or viscous substances that do not readily emerge from the diaphragm opening, as well as those substances that are hindered by the surface tension at the outlet through the diaphragm opening.
  • the FIG. 1 shows a measuring probe 1, which has an inner glass electrode 2 and a lying outside the glass electrode 2 reference electrode 3.
  • the reference electrode 3 is embedded in a second electrolyte in the form of a polymer electrolyte 4, which is present as a gel.
  • the glass electrode 2 has a diaphragm with pores formed by the glass wall of the glass bulb 5.
  • a first electrolyte 6 is arranged for example in the form of a liquid.
  • the measuring electrode 7 is arranged, which serves to derive the measured value in the form of a voltage at its socket-side end 8.
  • Such probes are, as shown, already commercially available and are with a gel-like polymer electrolyte as a second electrolyte, especially in food technology used for pH measurement in solids, since they are both robust and on the other hand allow diverse use without having to pay attention to the position of the probe in the measurement, since there is no risk of the gel polymer electrolyte 4 present as a gel.
  • the polymer electrolyte 4 can come into contact with a measuring substance outside the measuring probe through a diaphragm opening 9, which is formed between the glass bulb 5 and the housing wall 10 of the measuring probe.
  • a measuring substance contains ions
  • the potentiometric conditions in the measuring probe change, so that the pH of the measuring substance can be calculated or determined by means of reference values via a potentiometric voltage measured between the measuring electrode 7 and the reference electrode 3.
  • a gel-like second electrolyte 4 brings advantages, since a relatively large diaphragm opening 9 can be used, which scarcely clogs up due to microscopic contamination, as can happen in the case of fine-pore diaphragms, especially if protein-containing substances are measured.
  • impurities can still enter through the diaphragm opening 9 in the gel-like polymer electrolyte, as well as germs which can multiply there, and air pockets can also be formed which can falsify subsequent measurements.
  • the problem of cleaning is solved in that a pumping device is provided for the gel, which is arranged on the base 11 of the measuring probe 1 and in the FIGS. 3 and 4 is shown in more detail.
  • FIG. 3 shows a piston 12 which, as indicated by the arrow 13, by means of a drive wedge 14 under the action of the cone 15 of a drive screw 16 upwardly to the interior of the container 10 is slidable. Inside the container 10, the piston 12 thus displaces some of the second electrolyte 4, so that a certain amount of the second electrolyte, which is present as a polymer electrolyte, can be pushed out of the measuring probe through the opening 9 of the diaphragm and removed there.
  • the pumping device described would in itself allow only a single movement of the piston 12, but it is conceivable that this pushing movement can be divided into several steps, wherein after each measurement, the piston 12 is moved a little further to clean the probe.
  • a filling channel 19 which may serve, through a feed channel 20, some of the second electrolyte, the polymer electrolyte, into the container 10 from a container 21 which is shown schematically in the FIG FIG. 4 is shown, refill.
  • the filling channel may also be provided in the region designated by 24 between the piston 12 and the container wall
  • the feed line 20 can be closed with a screw cap and thereupon the pumping device is ready for a new cleaning process of the measuring probe.

Description

Die Erfindung ist auf dem Gebiet der Messtechnik anwendbar und zwar bei der Messung von Ladungsträgerkonzentrationen in Flüssigkeiten oder an Festkörpern. Insbesondere findet die Erfindung Anwendung bei der Messung eines ph-Wertes.The invention is applicable in the field of metrology and indeed in the measurement of charge carrier concentrations in liquids or solids. In particular, the invention finds application in the measurement of a pH value.

Die Erfindung bezieht sich auf eine Messsonde zur Messung einer Ladungsträgerkonzentration, insbesondere des ph-Wertes einer Messsubstanz, mit einer Glaselektrode, die einen ersten Elektrolyten sowie eine Messelektrode enthält und mit einem Behälter, der einen zweiten Elektrolyten enthält, welcher mit der Glaselektrode einerseits und mit einer Bezugselektrode andererseits in Verbindung steht, wobei der Behälter eine Diaphragmaöffnung aufweist, mittels dessen der zweite Elektrolyt mit der Messsubstanz in Verbindung treten kann.The invention relates to a measuring probe for measuring a charge carrier concentration, in particular the pH value of a measuring substance, comprising a glass electrode containing a first electrolyte and a measuring electrode and having a container containing a second electrolyte, which with the glass electrode on the one hand and a reference electrode on the other hand is in communication, wherein the container has a diaphragm opening, by means of which the second electrolyte can communicate with the measuring substance.

Als ph-Wert wird der negative dekadische Logarithmus der H+ - Ionenkonzentration (Protonenkonzentration) in einer Flüssigkeit bezeichnet. Diese Wasserstoffionenkonzentration lässt sich durch Zugabe von Basen oder Säuren zu Wasser in weiten Grenzen verändern. Der Messwert des ph gibt Aufschluss über die Stärke der Säure beziehungsweise Base.The ph value is the negative decadic logarithm of the H + ion concentration (proton concentration) in a liquid. This hydrogen ion concentration can be varied by addition of bases or acids to water within wide limits. The measured value of the ph gives information about the strength of the acid or base.

Der ph-Wert kann außer durch bekannte chemisch sensitive Farbindikatoren auch potentiometrisch gemessen werden. Es sind verschiedene Standardelektroden bekannt, deren Elektrodenspannung gegenüber einer Bezugselektrode unter dem Einfluss einer Messsubstanz in einen gemessenen ph-Wert umgerechnet werden kann.The pH value can also be measured potentiometrically in addition to known chemically sensitive color indicators. Various standard electrodes are known, whose electrode voltage can be converted to a reference electrode under the influence of a measuring substance in a measured ph value.

Eine bekannte labortechnisch angewandte Elektrode ist beispielsweise die Wasserstoffelektrode. In der Praxis und im Feldeinsatz hat sich dagegen die sogenannte Glaselektrode weithin bewährt wegen ihrer Robustheit. Eine derartige Glaselektrode weist prinzipiell einen Glasbehälter auf, dessen Glasaußenwand als Membrane ausgebildet ist und der in seinen Inneren einen ersten Elektrolyten enthält. In diesem ersten Elektrolyten befindet sich die sogenannte Mess- oder Ableitelektrode, deren Potential gegenüber einer Bezugselektrode gemessen wird. Die Bezugselektrode liegt außerhalb des Glasbehälters in einen zweiten Elektrolyten eingebettet, der mit der Glasmembran einerseits und mit der zu vermessenden Substanz über ein Diaphragma andererseits in Verbindung steht.A known electrode used in laboratory technology is, for example, the hydrogen electrode. In practice, and in field use, however, has the so-called glass electrode Well proven because of its robustness. Such a glass electrode has, in principle, a glass container whose glass outer wall is designed as a membrane and which contains a first electrolyte in its interior. In this first electrolyte is the so-called measuring or Ableitelektrode whose potential is measured relative to a reference electrode. The reference electrode is embedded outside the glass container in a second electrolyte, which communicates with the glass membrane on the one hand and with the substance to be measured via a diaphragm on the other.

Das Diaphragma muss so gewählt werden, dass einerseits die Messsubstanz in diesem Bereich mit dem zweiten Elektrolyten in Verbindung treten kann, dass andererseits der zweite Elektrolyt durch das Diaphragma nicht zur Gänze austritt. Ist der zweite Elektrolyt leicht flüssig, so muss darauf geachtet werden, dass er durch das Diaphragma nicht ausfließt. Das Diaphragma kann dann als poröse Membran ausgebildet sein. Bei schwerflüssigen beziehungsweise gelartigen Elektrolyten ist dieses Problem verringert und solche Elektroden können auch in verschiedenen Messpositionen eingesetzt werden, ohne dass der zweite Elektrolyt austritt. Das Diaphragma kann dann größere Öffnungen aufweisen oder als Öffnung ausgebildet sein.The diaphragm must be selected such that, on the one hand, the measuring substance in this area can come into contact with the second electrolyte, on the other hand, that the second electrolyte does not escape completely through the diaphragm. If the second electrolyte is slightly fluid, care must be taken that it does not flow out through the diaphragm. The diaphragm may then be formed as a porous membrane. In the case of heavy-liquid or gel-like electrolytes, this problem is reduced and such electrodes can also be used in different measuring positions without the second electrolyte emerging. The diaphragm may then have larger openings or be formed as an opening.

Dabei ergibt sich jedoch das Problem, dass die Messsubstanz, die bei jedem Messvorgang mit dem zweiten Elektrolyten in Verbindung tritt, diesen kontaminiert und dort in Resten verbleibt. Auch nimmt in dem zweiten Elektrolyten die CL- (Chlor)-Ionenkonzentration durch oft durchgeführte Messvorgänge langsam ab.
Aus der US-Patentschrift 2002027074 ist eine Messsonde zur Messung von ph-Werten bekannt, die eine Messelektrode, eine Bezugselektrode und einen zweiten Elektrolyten in Form eines Gels aufweist. Der zweite Elektrolyt ist in einem Behälter angeordnet, der ein Diaphragma in Form einer Öffnung aufweist, an der der gelförmige Elektrolyt nach außen mit einer Messsubstanz in Kontakt treten kann. Die Messelektrode ist ein ionensensitiver Feldeffekttransistor. Die Messsonde kann beispielsweise zur Messung des ph-Wertes von Reiskörnern genutzt werden, um deren Alter zu bestimmen.However, there is the problem that the measuring substance, which comes into contact with the second electrolyte during each measurement process, contaminates it and remains there in residues. Also participates in the second electrolyte, the CL - (chlorine) ion concentration by frequently performed measurement operations slowly.
From the US Patent 2002027074 For example, a measuring probe for measuring ph values is known, which has a measuring electrode, a reference electrode and a second electrolyte in the form of a gel. The second electrolyte is disposed in a container having a diaphragm in the form of an opening, at which the gel electrolyte can contact outwardly with a measuring substance. The measuring electrode is an ion-sensitive field effect transistor. For example, the probe can be used to measure the ph value of rice grains to determine their age.

Aus der europäischen Patentanmeldung Nr. 0922955 ist eine Messsonde bekannt mit einer ionenselektiven Glaselektrode, die ebenfalls mit einem Feldeffekttransistor gekoppelt ist.From European patent application no. 0922955 a measuring probe is known with an ion-selective glass electrode, which is also coupled to a field effect transistor.

Aus der deutschen Offenlegungsschrift 19857953 ist ebenfalls eine ph-Messsonde bekannt, bei der das Potential der Messelektrode mittels eines ionensensitiven Feldeffekttransistors verarbeitet wird. Dort steht ein Elektrolyt mittels eines Diaphragmas mit einer Messflüssigkeit in Verbindung. Weitere Messsonden sind beispielsweise in der DE 196 39 372 A1 und der WO 01/75430 A2 beschrieben.From the German patent application 19857953 a ph probe is also known in which the potential of the measuring electrode is processed by means of an ion-sensitive field effect transistor. There, an electrolyte is connected by means of a diaphragm with a measuring liquid. Further measuring probes are for example in the DE 196 39 372 A1 and the WO 01/75430 A2 described.

Der Erfindung liegt die Aufgabe zugrunde, bei einer Messsonde der eingangs genannten Art die mögliche Einsatzdauer bei gleichbleibender Messqualität möglichst zu verlängern oder eine Möglichkeit zu schaffen, eine derartige Messsonde mit geringem Aufwand weiterverwendbar zu machen.The invention has for its object to extend as far as possible in a measuring probe of the type mentioned the possible duration of use with the same quality of measurement or to provide a way to make such a probe with little effort reusable.

Die Aufgabe wird gemäß Anspruch 1 dadurch gelöst, dass der Behälter eine Pumpeinrichtung zur Beförderung einer Menge des zweiten Elektrolyten in das Innere des Behälters aufweist.The object is achieved according to claim 1, characterized in that the container has a pumping device for conveying a quantity of the second electrolyte into the interior of the container.

Die Pumpeinrichtung kann eine bestimmte Menge des zweiten Elektrolyten in das Innere des Behälters befördern, so dass eine überschüssige Menge aus der Diaphragmaöffnung des austritt. Diese austretende Menge des zweiten Elektrolyten fließt entweder ab oder kann außen an der Messsonde entfernt werden, so dass an dem Diaphragma für nachfolgende Messungen der zweite Elektrolyt in unverbraüchter Form zur Verfügung steht. Auch Verschmutzungen werden durch den austretenden zweiten Elektrolyten aus der Diaphragmaöffnung mit ausgeschwemmt.The pumping device can convey a certain amount of the second electrolyte into the interior of the container, so that an excess amount emerges from the diaphragm opening of the container. This exiting amount of the second electrolyte either flows off or can be removed on the outside of the measuring probe, so that the second electrolyte is available in an unobstructed form at the diaphragm for subsequent measurements. Also contaminants are washed out by the exiting second electrolyte from the diaphragm opening with.

Die Erfindung sieht vor, dass der Behälter im Bereich seiner Wand einen mit dem zweiten Elektrolyten gefüllten Kanal aufweist, in den ein Körper einschiebbar ist, um wenigstens einen Teil des in dem Kanal befindlichen zweiten Elektrolyten in das Innere des Behälters zu befördern.The invention provides that the container has, in the region of its wall, a channel filled with the second electrolyte, into which a body can be inserted in order to convey at least part of the second electrolyte located in the channel into the interior of the container.

Erfindungsgemäß ist eine Antriebseinrichtung vorgesehen , die eine Verschiebung des Körpers zum Inneren des Behälters bewirkt und dass die Antriebseinrichtung zum Nachfüllen des zweiten Elektrolyten von dem Körper entkoppelbar ist.According to the invention a drive device is provided which causes a displacement of the body to the interior of the container and that the drive means for replenishing the second electrolyte is decoupled from the body.

Dadurch, dass die Antriebseinrichtung zum Nachfüllen des zweiten Elektrolyten von dem Körper entkoppelbar ist, ist es beispielsweise möglich, den zweiten Elektrolyten unter Druck in den Behälter einzuspritzen und dadurch den Körper in dem Kanal durch den hydrostatischen Druck des zweiten Elektrolyten in seine Ausgangsposition zurückzutreiben.By virtue of the fact that the drive device can be decoupled from the body for refilling the second electrolyte, it is possible, for example, to inject the second electrolyte under pressure into the container and thereby to return the body in the channel to its initial position by the hydrostatic pressure of the second electrolyte.

Eine besonders einfache konstruktive Ausgestaltung der Erfindung besteht darin, dass der Körper ein Kolben ist, der in einem Hohlzylinder gleitet und dass die Antriebseinrichtung mit einer Schraube gebildet ist.A particularly simple structural embodiment of the invention is that the body is a piston which slides in a hollow cylinder and that the drive means is formed with a screw.

Durch die Verwendung einer Schraube kann die Antriebseinrichtung ohne größere Kraftanwendung betrieben werden, da hierdurch eine starke Untersetzung stattfindet. Das zu verdrängende Volumen in dem Behälter ist jedoch wegen der üblicherweise geringen Ausdehnungen der Diaphragmaöffnung sehr gering, so dass der Kolben keinen langen Weg zurücklegen muss.By using a screw, the drive device can be operated without major application of force, as this takes place a strong reduction. However, the volume to be displaced in the container is very small because of the usually small dimensions of the diaphragm opening, so that the piston does not have to travel a long way.

Besonders vorteilhaft wird die Antriebseinrichtung derart gestaltet, dass die Achse der Schraube senkrecht zu der Achse des Hohlzylinders verläuft und dass die Schraube an ihrer Spitze einen Konus aufweist, an dem der Kolben abgestützt ist und dessen Verschiebung in Richtung der Achse der Schraube durch Keilwirkung eine Verschiebung des Kolbens bewirkt.Particularly advantageously, the drive device is designed such that the axis of the screw is perpendicular to the axis of the hollow cylinder and that the screw has at its tip a cone on which the piston is supported and its displacement in the direction of the axis of the screw by wedge action a shift of the piston causes.

Dadurch ist nur eine besonders geringe Kraftanwendung bei der Betätigung der Schraube zum Antrieb des Kolbens notwendig und der Vorschub des Kolbens kann besonders genau dosiert werden, um gerade so viel von dem zweiten Elektrolyten durch die Diaphragmaöffnung hindurchzudrücken, dass eine ausreichende Reinigung des Diaphragmas und Erneuerung des zweiten Elektrolyten stattfindet.As a result, only a particularly small application of force in the operation of the screw for driving the piston is necessary and the advance of the piston can be metered very precisely to push just as much of the second electrolyte through the diaphragm opening that sufficient cleaning of the diaphragm and renewal of the second electrolyte takes place.

Um die Messsonde dauerhaft betreiben zu können, muss wiederholt eine Menge des zweiten Elektrolyten in den Füllkanal nachfüllbar sein. Zu diesem Zweck erweist es sich als sinnvoll, dass der Füllkanal mit einem außen verschließbaren Speisekanal verbunden ist, durch den der Messsonde der zweite Elektrolyt zugeführt werden kann.In order to be able to operate the measuring probe permanently, a quantity of the second electrolyte must be repeatedly refillable into the filling channel. For this purpose, it proves to be useful that the filling channel is connected to an externally closable feed channel, through which the probe the second electrolyte can be supplied.

In diesem Fall kann der Körper mindestens einmal in den Behälter eingeschoben werden, um eine Menge des zweiten Elektrolyten zu verdrängen oder in den Behälter hineinzubefördern und danach kann beim Zurückziehen des Körpers durch den Speisekanal eine Menge des zweiten Elektrolyten in den Füllkanal und von dort in den Behälter nachbefördert werden.In this case, the body may be inserted at least once into the container to displace or feed into the container a quantity of the second electrolyte, and thereafter upon retraction of the body through the feed channel, a quantity of the second electrolyte may be introduced into and from the filling channel Container nachbefördert be.

Die erfindungsgemäße Konstruktion der Messsonde erweist sich besonders dann als vorteilhaft, wenn der zweite Elektrolyt durch ein Gel gebildet ist. Dann ist gewährleistet, dass die Messsonde sich in jeder Position betreiben lässt, ohne dass eine Menge des zweiten Elektrolyten durch die Öffnung des Diaphragmas austritt. Dennoch weist das Gel als Elektrolyt alle notwendigen Eigenschaften für die Ionenleitung in einer ph-Messsonde auf. Es ist neben der Verwendung thixiotroper Stoffe (Gele) auch denkbar, schwer flüssige oder zähflüssige Stoffe zu verwenden, die nicht ohne weiteres aus der Diaphragmaöffnung austreten,sowie solche Stoffe, die durch die Oberflächenspannung am Austritt durch die Diaphragmaöffnung gehindert sind.The inventive construction of the measuring probe proves to be particularly advantageous if the second electrolyte is formed by a gel. Then it is ensured that the probe can be operated in any position without a lot of the second electrolyte escaping through the opening of the diaphragm. Nevertheless, the gel as electrolyte has all the necessary properties for ionic conduction in a pH measuring probe. It is in addition to using thixiotroper Substances (gels) also conceivable to use difficult liquid or viscous substances that do not readily emerge from the diaphragm opening, as well as those substances that are hindered by the surface tension at the outlet through the diaphragm opening.

Im folgenden wird die Erfindung anhand eines Ausführungsbeispiels in einer Zeichnung gezeigt und nachfolgend beschrieben. Dabei zeigt

  • Figur 1 eine erfindungsgemäße Messsonde schematisch im Längsschnitt,
  • Figur 2 einen vergrößerten Ausschnitt aus der Figur 1, der dort mit a bezeichnet ist,
  • Figur 3 einen vergrößerten Ausschnitt aus der Figur 1, der dort mit b bezeichnet ist, wobei die Phase dargestellt ist, in der der zweite Elektolyt verdrängt wird,
  • Figur 4 denselben Ausschnitt wie Figur 3, wobei die Phase dargestellt ist, in der eine Menge des zweiten Elektrolyten nachgefüllt wird.
In the following the invention with reference to an embodiment in a drawing is shown and described below. It shows
  • FIG. 1 a measuring probe according to the invention schematically in longitudinal section,
  • FIG. 2 an enlarged section of the FIG. 1 which is there denoted by a,
  • FIG. 3 an enlarged section of the FIG. 1 denoted by b, representing the phase in which the second electrolyte is displaced,
  • FIG. 4 same section as FIG. 3 , wherein the phase is shown, in which an amount of the second electrolyte is replenished.

Die Figur 1 zeigt eine Messsonde 1, die eine innenliegende Glaselektrode 2 sowie eine außerhalb der Glaselektrode 2 liegende Bezugselektrode 3 aufweist. Die Bezugselektrode 3 ist in einen zweiten Elektrolyten in Form eines Polymerelektrolyten 4 eingebettet, der als Gel vorliegt.The FIG. 1 shows a measuring probe 1, which has an inner glass electrode 2 and a lying outside the glass electrode 2 reference electrode 3. The reference electrode 3 is embedded in a second electrolyte in the form of a polymer electrolyte 4, which is present as a gel.

Die Glaselektrode 2 weist ein Diaphragma mit Poren auf, das durch die Glaswand des Glaskolbens 5 gebildet ist. In dem Glaskolben 5 ist ein erster Elektrolyt 6 beispielsweise in Form einer Flüssigkeit angeordnet. In diesem ersten Elektrolyten ist die Messelektrode 7 angeordnet, die zur Ableitung des Messwertes in Form einer Spannung an ihrem sockelseitigen Ende 8 dient.The glass electrode 2 has a diaphragm with pores formed by the glass wall of the glass bulb 5. In the glass bulb 5, a first electrolyte 6 is arranged for example in the form of a liquid. In this first electrolyte, the measuring electrode 7 is arranged, which serves to derive the measured value in the form of a voltage at its socket-side end 8.

Derartige Messsonden sind, wie dargestellt, im Handel bereits erhältlich und werden mit einem gelartigen Polymerelektrolyten als zweiten Elektrolyten insbesondere in der Lebensmitteltechnik zur ph-Messung bei Festkörpern eingesetzt, da sie einerseits robust sind und andererseits vielfältigen Einsatz erlauben ohne dass auf die Lage der Sonde bei der Messung geachtet zu werden braucht, da keine Gefahr für das Austreten des als Gel vorliegenden Polymerelektrolyten 4 besteht.Such probes are, as shown, already commercially available and are with a gel-like polymer electrolyte as a second electrolyte, especially in food technology used for pH measurement in solids, since they are both robust and on the other hand allow diverse use without having to pay attention to the position of the probe in the measurement, since there is no risk of the gel polymer electrolyte 4 present as a gel.

Der Polymerelektrolyt 4 kann durch eine Diaphragmaöffnung 9, die zwischen dem Glaskolben 5 und der Gehäusewand 10 der Messsonde gebildet ist, mit einer Messsubstanz außerhalb der Messsonde in Kontakt treten. Durch einen solchen Kontakt ändern sich, wenn die Messsubstanz Ionen enthält, die potentiometrischen Verhältnisse in der Messsonde, so dass über eine zwischen der Messelektrode 7 und der Bezugselektrode 3 hochohmig gemessene potentiometrische Spannung der ph-Wert der Messsubstanz errechnet oder mittels Referenzwerten ermittelt werden kann.The polymer electrolyte 4 can come into contact with a measuring substance outside the measuring probe through a diaphragm opening 9, which is formed between the glass bulb 5 and the housing wall 10 of the measuring probe. By such a contact, if the measuring substance contains ions, the potentiometric conditions in the measuring probe change, so that the pH of the measuring substance can be calculated or determined by means of reference values via a potentiometric voltage measured between the measuring electrode 7 and the reference electrode 3.

Die Verwendung eines gelartigen zweiten Elektrolyten 4 bringt einerseits Vorteile, da eine relativ große Diaphragmaöffnung 9 verwendet werden kann, die durch mikroskopische Verunreinigungen kaum verstopft, wie dies bei feinporigen Diaphragmen geschehen kann, insbesondere wenn eiweißhaltige Substanzen vermessen werden.The use of a gel-like second electrolyte 4 on the one hand brings advantages, since a relatively large diaphragm opening 9 can be used, which scarcely clogs up due to microscopic contamination, as can happen in the case of fine-pore diaphragms, especially if protein-containing substances are measured.

Andererseits können dennoch durch die Diaphragmaöffnung 9 Verunreinigungen in den gelartigen Polymerelektrolyten gelangen sowie Keime, die sich dort vermehren können und es können auch Lufteinschlüsse entstehen, die nachfolgende Messungen verfälschen können.On the other hand, impurities can still enter through the diaphragm opening 9 in the gel-like polymer electrolyte, as well as germs which can multiply there, and air pockets can also be formed which can falsify subsequent measurements.

Es ist versucht worden, derartige Messsonden dadurch zu regenerieren, dass sie mit heißem Wasser behandelt werden, wodurch der zweite Elektrolyt aufquillt und sich teilweise aus der Diaphragmaöffnung 9 herausschiebt.Attempts have been made to regenerate such probes by treating them with hot water, causing the second electrolyte to swell and partially slide out of the diaphragm opening 9.

Dies ist jedoch mit üblichen Messsonden wegen der komplizierten mit ihnen verbundenen Elektronik nicht möglich und außerdem nimmt durch die mit einer solchen Reinigung verbundene Wasseraufnahme die Chlor-Ionenkonzentration in dem Gel und die Masse des Polymerelektrolyten ab. In entstehenden Lufteinschlüssen können sich insbesondere Verschmutzungen und Keime sammeln und vermehren. Dies hat zur Folge, dass bei nachfolgenden Messungen die Messsubstanz weiter durch die Diaphragmaöffnung 9 zum Inneren des Behälters der Sonde eindringen muss, bevor eine genaue Messung ermöglicht ist. Die Ansprechzeit der Sonde wird hierdurch verlängert.However, this is not possible with conventional probes because of the complicated electronics associated with them, and moreover As a result of the water absorption associated with such a purification, the chlorine ion concentration in the gel and the mass of the polymer electrolyte decreases. Contaminations and germs can accumulate and multiply in resulting air pockets. This has the consequence that in subsequent measurements, the measuring substance must continue to penetrate through the diaphragm opening 9 to the interior of the container of the probe before an accurate measurement is possible. The response time of the probe is thereby extended.

Bei der hier vorliegenden erfindungsgemäßen Sonde ist das Problem der Reinigung dadurch gelöst, dass eine Pumpeinrichtung für das Gel vorgesehen ist, die am Sockel 11 der Messsonde 1 angeordnet ist und die in den Figuren 3 und 4 näher gezeigt ist.In the present invention probe, the problem of cleaning is solved in that a pumping device is provided for the gel, which is arranged on the base 11 of the measuring probe 1 and in the FIGS. 3 and 4 is shown in more detail.

Die Figur 3 zeigt einen Kolben 12, der, wie durch den Pfeil 13 angedeutet ist, mittels eines Antriebskeils 14 unter der Wirkung des Konus 15 einer Antriebsschraube 16 nach oben zum Inneren des Behälters 10 schiebbar ist. Im Inneren des Behälters 10 verdrängt der Kolben 12 damit etwas von dem zweiten Elektrolyten 4, so dass sich eine gewisse Menge des zweiten Elektolyten, der als Polymerelektrolyt vorliegt, durch die Öffnung 9 des Diaphragmas aus der Messsonde herausschiebt und dort entfernt werden kann.The FIG. 3 shows a piston 12 which, as indicated by the arrow 13, by means of a drive wedge 14 under the action of the cone 15 of a drive screw 16 upwardly to the interior of the container 10 is slidable. Inside the container 10, the piston 12 thus displaces some of the second electrolyte 4, so that a certain amount of the second electrolyte, which is present as a polymer electrolyte, can be pushed out of the measuring probe through the opening 9 of the diaphragm and removed there.

Dies geschieht dadurch, dass die Antriebsschraube 16 in einem Gewinde innerhalb des Kanals 17 durch eine Schraubbewegung in Richtung des Pfeils 18 angetrieben wird.This happens because the drive screw 16 is driven in a thread within the channel 17 by a screwing movement in the direction of the arrow 18.

Die beschriebene Pumpeinrichtung würde an sich nur eine einmalige Bewegung des Kolbens 12 erlauben, wobei jedoch denkbar ist, dass diese Schubbewegung in mehrere Schritte geteilt werden kann, wobei nach jeder Messung der Kolben 12 ein Stück weit weiter bewegt wird, um die Messsonde zu reinigen.The pumping device described would in itself allow only a single movement of the piston 12, but it is conceivable that this pushing movement can be divided into several steps, wherein after each measurement, the piston 12 is moved a little further to clean the probe.

Es ist jedoch vorteilhaft, in dem Kolben 12 einen Füllkanal 19 vorzusehen, der dazu dienen kann, durch einen Speisekanal 20 etwas von dem zweiten Elektrolyten, dem Polymerelektrolyten, in den Behälter 10 aus einem Behälter 21, der nur schematisch in der Figur 4 dargestellt ist, nachzufüllen. Alternativ zu der abgebildeten Variante kann der Füllkanal auch in dem mit 24 bezeichneten Bereich zwischen dem Kolben 12 und der Behälterwand vorgesehen seinHowever, it is advantageous to provide in the piston 12 a filling channel 19 which may serve, through a feed channel 20, some of the second electrolyte, the polymer electrolyte, into the container 10 from a container 21 which is shown schematically in the FIG FIG. 4 is shown, refill. As an alternative to the illustrated variant, the filling channel may also be provided in the region designated by 24 between the piston 12 and the container wall

Wird durch den Speisekanal 20 etwas von dem Polymerelektrolyten in den Füllkanal 19 hineingedrückt, so gelangt diese Menge in das Innere des Behälters 10 und zwar im Bereich der Stirnfläche 22 des Kolbens 12. Der hier einströmende zweite Polymerelekrolyt drängt den Kolben 12 entgegen der durch den Pfeil 13 dargestellten Richtung zurück, wenn die Schraube 16 in dem Kanal 17 durch Zurückschrauben entgegen der durch den Pfeil 18 dargestellten Richtung wegbewegt worden ist. Vorteilhaft hierbei ist, dass der zweite Elektrolyt 4 genau in den Bereich eingebracht wird, aus dem der Kolben 12 zurückbewegt wird, so dass keine Lufteinschlüsse entstehen können.If some of the polymer electrolyte is pressed into the filling channel 19 through the feed channel 20, this quantity passes into the interior of the container 10 in the region of the end face 22 of the piston 12. The second polymer electrolyte flowing in here urges the piston 12 counter to that indicated by the arrow 13, when the screw 16 in the channel 17 has been moved away by screwing it back in the direction shown by the arrow 18. The advantage here is that the second electrolyte 4 is accurately introduced into the area from which the piston 12 is moved back, so that no air pockets can arise.

Nach dem Nachfüllen des zweiten Elektrolyten kann die Speiseleitung 20 mit einem Schraubdeckel verschlossen werden und darauf steht die Pumpeinrichtung für einen neuen Reinigungsvorgang der Messsonde bereit.After refilling the second electrolyte, the feed line 20 can be closed with a screw cap and thereupon the pumping device is ready for a new cleaning process of the measuring probe.

Claims (9)

  1. Measuring probe (1) for measuring a charge carrier concentration, in particular the pH value of a measurement substance, with a glass electrode (2) which contains a first electrolyte (6) as well as a meter electrode (7), and with a container (10) which contains a second electrolyte (4), which is in contact with the glass electrode (2) on the one hand and to a reference electrode (3) on the other hand, wherein the container has a diaphragm opening, by means of which the second electrolyte (4) can come into contact with the measurement substance,
    characterised in that
    the container has a pump device (12, 14, 16) for transporting a quantity of the second electrolyte (4) into the interior of the container (10), wherein
    the container (10), in the area of its wall, has a channel which is filled with the second electrolyte, and into which a body can be pushed in order to convey at least part of the second electrolyte that is located in the channel into the interior of the container,
    characterised in that
    a driving device (15, 16) is provided, which displaces the body (12) towards the interior of the container (10), and that the driving device can be decoupled from the body (12) in order to allow refilling with the second electrolyte (4).
  2. Measuring probe (1) according to claim 1, characterised in that the body (12) can be pulled back, at least partially, from out of the interior of the container (10), and that a filling channel (19) is provided, through which a quantity of the second electrolyte (4) can be introduced at a side of the body (12) that faces the interior of the container.
  3. Measuring probe (1) according to claim 2, characterised in that the filling channel (12) runs through the interior of the body.
  4. Measuring probe (1) according to claim 2, characterised in that the filling channel is formed between the body (12) and the wall of the container (10).
  5. Measuring probe (1) according to claim 1, characterised in that the body (12) is a piston that slides in a hollow cylinder (23), and that the driving device (15, 16) is formed with a screw (16).
  6. Measuring probe (1) according to claim 5, characterised in that the axis of the screw (16) runs perpendicular to the axis of the hollow cylinder (23), and that the screw (16) has at its tip a taper (15) on which the piston (12) is supported and which, when it is displaced in the direction of the screw axis (16), causes a displacement of the piston (12), through a wedge action.
  7. Measuring probe (1) according to claim 5 and 3, characterised in that the filling channel (19) is connected to a feed channel (20) that can be sealed on the outside, through which the second electrolyte (4) can be supplied to the measuring probe.
  8. Measuring probe (1) according to one of the preceding claims, characterised in that the second electrolyte (4) is a gel.
  9. Method for operating a measuring probe (1) according to one of the preceding patent claims, characterised in that where necessary, prior to a measurement either a quantity of the second electrolyte (4) is conveyed into the interior of the container (10) or a quantity of the second electrolyte (4) that is located there is displaced, with the result that some of the second electrolyte emerges from the container (10), through the diaphragm opening (9).
EP03771059A 2002-07-25 2003-07-18 Device and method for generating pressure in the electrolytes of a reference electrode Expired - Lifetime EP1525460B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE2002133905 DE10233905A1 (en) 2002-07-25 2002-07-25 Measuring probe for measuring a carrier concentration and method for its operation
DE10233905 2002-07-25
PCT/EP2003/007886 WO2004011920A1 (en) 2002-07-25 2003-07-18 Device and method for generating pressure in the electrolytes of a reference electrode

Publications (2)

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EP1525460A1 EP1525460A1 (en) 2005-04-27
EP1525460B1 true EP1525460B1 (en) 2008-11-19

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Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE8906234U1 (en) * 1989-05-20 1989-07-06 Neukum Elektronik Gmbh, 7541 Straubenhardt, De
EP0414033B1 (en) * 1989-08-18 1994-05-04 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. Method for continuous electrolyte transfer and reference electrode system
DE19639372C2 (en) * 1996-09-25 1999-12-09 Gerrit Peters Device for electrochemical measuring processes
GB9726348D0 (en) * 1997-12-13 1998-02-11 Eastman Kodak Co Ion concentration and pH measurement
DE19857953C2 (en) * 1998-12-16 2001-02-15 Conducta Endress & Hauser Device for measuring the concentration of ions in a measuring liquid
US6599409B1 (en) * 1999-06-08 2003-07-29 Broadley Technologies Corporation Reference electrode having a microfluidic flowing liquid junction
US6495012B1 (en) * 2000-03-31 2002-12-17 The Foxboro Company Sensor for electrometric measurement

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DE50310808D1 (en) 2009-01-02
EP1525460A1 (en) 2005-04-27
WO2004011920A1 (en) 2004-02-05
DE10233905A1 (en) 2004-02-12

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